Make sure that a = 1 (if a ≠ 1, multiply through the equation by before proceeding).Put the equation into the form ax 2 + bx = – c.Ī third method of solving quadratic equations that works with both real and imaginary roots is called completing the square. Since the discriminant b 2 – 4 ac is negative, this equation has no solution in the real number system.īut if you were to express the solution using imaginary numbers, the solutions would be. The quadratic formula can also be used to solve quadratic equations whose roots are imaginary numbers, that is, they have no solution in the real number system. Since the discriminant b 2 – 4 ac is 0, the equation has one root. Then substitute 1, 2, and –2 for a, b, and c, respectively, in the quadratic formula and simplify. In Example, the quadratic formula is used to solve an equation whose roots are not rational. Then substitute 1 (which is understood to be in front of the x 2), –5, and 6 for a, b, and c, respectively, in the quadratic formula and simplify.īecause the discriminant b 2 – 4 ac is positive, you get two different real roots.Įxample produces rational roots. No real root if the discriminant b 2 – 4 ac is a negative number.One real root if the discriminant b 2 – 4 ac is equal to 0.Two different real roots if the discriminant b 2 – 4 ac is a positive number.A quadratic equation with real numbers as coefficients can have the following: The discriminant is the value under the radical sign, b 2 – 4 ac. These three possibilities are distinguished by a part of the formula called the discriminant. When using the quadratic formula, you should be aware of three possibilities. Where a is the numeral that goes in front of x 2, b is the numeral that goes in front of x, and c is the numeral with no variable next to it (a.k.a., “the constant”). A second method of solving quadratic equations involves the use of the following formula:Ī, b, and c are taken from the quadratic equation written in its general form of This is generally true when the roots, or answers, are not rational numbers. Many quadratic equations cannot be solved by factoring. To check, 2 x 2 + 2 x – 1 = x 2 + 6 x – 5 X 2 – 6 x = 16 becomes x 2 – 6 x – 16 = 0īoth values, 8 and –2, are solutions to the original equation.Ī quadratic with a term missing is called an incomplete quadratic (as long as the ax 2 term isn't missing).įirst, simplify by putting all terms on one side and combining like terms.
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